Application-Layer Gateways

Application-layer gateways improve security by examining all application layers, bringing context information into the decision-making process. However, the method they use to do this disrupts the client/server model, reducing scalability. Ordinarily, a client sends requests for information or action according to a specific protocol, and the server responds, all in one connection. With application-layer gateways, each client/server communications requires two connections: one from a client to a proxy, and one from a proxy to a server. In addition, each proxy requires a different process (or daemon), making support for new applications a problem.

Application-layer gateways have the following advantages and disadvantages:

Application-Layer Gateway Advantages and Disadvantages